Double Side Polishing Machine

ABSTRACT

The present invention is to provide a double side polishing machine which can apply a load by the upper lapping plate uniformly to works and the deflection of the upper lapping plate is restrained, which comprises a rotatable lower lapping plate, a rotatable upper lapping plate and movable to the lower lapping plate by an elevation mechanism, carriers which are put between the lower lapping plate and the upper lapping plate and in which a plurality of works are mounted, and a rotation and revolution mechanism for rotating and revolving the carriers between the lower lapping plate and the upper lapping plate, wherein a supporting plate for upper lapping plate which suspends the upper lapping plate is connected to an upper portion of a coupling mechanism provided oscillatably on a vertically movable supporting rod of the elevation mechanism, and an oscillation fulcrum of the coupling mechanism is located at approximately same height to a polishing surface of the upper polishing plate.

TECHNICAL FIELD

This invention relates to a double side polishing machine for polishinga work such as a semiconductor wafer and a photomask.

BACKGROUND ART

A double side polishing machine disclosed in JP 2002-120143 A is that anupper lapping plate is supported by a cylinder for suspending in whichfluid is a supporting medium so that a processing load can be applieduniformly to a work, namely that a plurality of supporting mechanismssupporting the upper lapping plate with fluid as supporting medium areprovided at specific intervals around a center axis line of the upperlapping plate between a suspender for the lapping plate mounted on anelevator for rising and falling the upper lapping plate and the upperlapping plate.

A polishing machine disclosed in JP 2002-154049 A is that a supportingdisc whose size is similar to an upper lapping plate is provided on afront end of a rod of a cylinder device for elevating the upper lappingplate, and that deflection of the upper lapping plate is prevented bysupporting between the supporting disc and the upper lapping plate by aplurality of supporting rods.

JP 2002-346918 A discloses a double side polishing machine which isprovided with a lower lapping plate provided rotatably, an upper lappingplate provided above the lower lapping plate movably up and down androtatably, a sun gear provided rotatably at a center position of thelower lapping plate, an internal gear provided rotatably at an outerperipheral side of the lower lapping plate, and carriers which canrotate and revolve with rotation of both gears by engaging with the sungear and the internal gear and which can hold works, wherein an armconnected with a power source is provided above the upper lapping plate,a drive pin projecting outward in a radial direction is provided eitheron an outer peripheral end portion of the arm or on an outer peripheralend portion of the upper lapping plate, a drive bracket having a groovein which the drive pin is engaged with a specific clearance in arotating direction is provided either on an outer peripheral end portionof the arm or on an outer peripheral end portion of the upper lappingplate, and a drive transmission mechanism for transmitting a drive forcein the arm side to the upper lapping plate is constituted by the drivepin and the drive bracket. Besides, it discloses that the arm and theupper lapping plate are connected removably relatively by a suspendedmember.

SUMMARY OF THE INVENTION

As disclosed in the above mentioned references, it is a special problemin the double side polishing machine that a load by the upper lappingplate is applied uniformly to works and the deflection of the upperlapping plate is prevented. Furthermore, in recent years, because highaccuracy for polishing is required, the above problem must be solved inthe highest accuracy condition.

Besides, because a suspended position as an oscillation fulcrum of theupper lapping plate is at an end portion of the rod of the cylinder,distance between the upper lapping plate and the oscillation fulcrum islarge and as a result, disadvantage such that variability of the upperlapping plate by variability of the rod is large is arisen.

Accordingly, the present invention is to provide a double side polishingmachine in which load to works is applied equally by preventingvariability and deflection of the upper lapping plate.

Therefore, the present invention is a double side polishing machinecomprising a rotatable lower lapping plate, a rotatable upper lappingplate and movable to the lower lapping plate by an elevation mechanism,carriers which are put between the lower lapping plate and the upperlapping plate and in which a plurality of works are mounted, and arotation and revolution mechanism for rotating and revolving thecarriers between the lower lapping plate and the upper lapping plate,wherein a supporting plate for upper lapping plate which suspends theupper lapping plate is connected to an upper portion of a couplingmechanism provided oscillatably on a vertically movable supporting rodof the elevation mechanism, and an oscillation fulcrum of the couplingmechanism is located at approximately same height to a polishing surfaceof the upper polishing plate. Namely, the oscillation fulcrum ispositioned on a standard plane expanding from the polishing surface ofthe upper polishing plate.

Thus, because the oscillation fulcrum of the upper lapping plate islocated at approximately same height to the polishing surface thereof,distance between suspended positions of the upper polishing plate andthe oscillation fulcrum can be made to a minimum, so that thevariability of the upper polishing plate can be made to a minimum.

Besides, it is preferred that said upper polishing plate is suspended onthe supporting plate outward in a radial direction from a center ofgravity in one side of the polishing surface of the upper polishingplate. Thus, as the prior upper polishing plate is in a doughnut-shape,it has a tendency of warping so that the outer peripheral portion goesdown, but because the upper polishing plate is supported outward fromthe center of polishing surface thereof, the outer peripheral portionthereof can be prevented going down and an inner peripheral portionthereof is difficult to go down, so that the deflection of the upperpolishing plate can be prevented.

Furthermore, it is preferred that the supporting plate has a pluralityof reinforcement ribs extending along the radiation direction. Thus, asstrength of the supporting plate can be increased, the deflection of theupper lapping plate due to the deflection of the supporting plate can beprevented.

Moreover, it is preferred that the coupling mechanism is agyro-mechanism and a center position of the gyro-mechanism is positionedat approximately same height to the polishing surface of the upperlapping plate. By this manner, load bias of the upper lapping plate dueto a fine gap and an inclination of the supporting rod can be prevented.

Besides, it is preferred that the upper lapping plate can be rotatableby an upper lapping plate rotation mechanism for rotating the supportingrod and the upper lapping plate rotation mechanism is provided on theelevation mechanism. It has an effect such that a lower lapping platerotation mechanism can be simplified by providing the upper lappingplate rotation mechanism separately from the lower lapping platerotation mechanism. Thus, mechanical or structural resonance between theupper and the lower lapping plates can be prevented.

Due to the abovementioned constitution, according to the presentinvention, since an oscillation fulcrum of a coupling mechanism holdinga support plate for upper lapping plate is positioned on anapproximately same as a polishing surface of the upper lapping plate,distance between the polishing surface of the upper polishing plate andthe oscillation fulcrum can be made to a minimum, so that an area ofoscillation can be smaller and then polishing accuracy can be increased.Besides, positions suspending the upper polishing plate are positionedoutward from a center of gravity in one side thereof and reinforcementribs are formed on the supporting plate, so that deflection of the upperlapping plate can be prevented and load applied to works can be madeuniformly and as a result, best accuracy double side polishing can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a double side polishing machineaccording to an embodiment of the present invention.

FIG. 2 is an enlarged diagram showing around upper and lower lappingplates of the double side polishing machine according to the embodimentof the present invention.

FIG. 3 is an enlarged diagram of the upper polishing plate of the doubleside polishing machine according to the embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention is explained byreferring drawings.

A double side polishing machine 1 according to an embodiment of thepresent invention comprises an upper polishing plate 2 and a lowerpolishing plate 3 between which a plurality of carriers not shown infigures installing plural works are put, and a sun gear 4 and aninternal gear 5 with which the carriers are engaged in order to rotateand revolve.

The lower polishing plate 3 is secured on a supporting plate for lowerpolishing plate 6 to be held and rotated via a rotatable cylindricalshaft 7 on which the supporting plate 6 is secured. A rotation shaft 8passing though the rotatable cylindrical shaft 7 is provided inside therotatable cylindrical shaft 7, a closed-end and cylindrical sun gearportion 9 is secured at a front end of the rotation shaft 8, and thenthe sun gear 4 formed on an outer peripheral surface of the sun gearportion 9 is rotated with rotation of the rotation shaft 8. Besides, acylindrical holder portion 10 for receiving axial direction load appliedon the rotatable cylindrical shaft 7 and for holding it rotatably isprovided outside the rotatable cylindrical shaft 7. Further, a rotatableouter cylindrical portion 11 for driving the internal gear 5 is providedrotatably on an outer peripheral portion of the cylindrical holderportion 10, a peripheral wall portion for internal gear 12 extending toa radically outer peripheral of the rotatable outer cylindrical portion11 is formed on the rotatable outer cylindrical portion 11, and theinternal gear 5 is secured on an upper end inner peripheral edge of theperipheral wall 12.

Further, the rotatable outer cylindrical portion 11 is rotated via agear mechanism 13 by a motor 14 and the rotatable cylindrical portion 7is rotated via a coupling mechanism 16 such as belts by a motor 17.Besides, the rotation shaft 8 is rotated via a gear mechanism 18 bycoupling with the rotatable cylindrical shaft 7.

The upper polishing plate 2 is movable up and down by means of theelevation mechanism 19. The elevation mechanism 19 comprises a firstlift mechanism 20 for moving the upper polishing plate 2 along a largescale up and down, a second lift mechanism 21 for moving the upperpolishing plate 2 along a small scale up and down and a supporting rod30 for supporting the upper polishing plate 2, and further comprises amotor 22 and a gear mechanism 23 for rotating the supporting rod 30.

As shown in FIGS. 2 and 3, the upper polishing plate 2 is secured on asupporting plate for upper polishing plate 50 secured on agyro-mechanism 40 via the gyro mechanism 40 provided on a front end of acylindrical holding portion 31 in which the rotatable supporting rod 30is fitted. Secured points S between the supporting plate 50 and theupper polishing plate 2 are set outward at a specific distance d awayfrom a gravity point O in sectional view of one side in a radialdirection of the upper polishing plate 2. Thus, though load is appliedto the upper polishing plate 2 so that an inner peripheral edge portiongoes down, this load is applied in a direction such that the innerperipheral edge portion of the upper polishing plate 2 is compressed,deflection of the upper polishing plate 2 can be prevented more than acase that load is applied to the outer peripheral edge portion.

Moreover, a plurality of reinforcement ribs 51 extending along theradical direction from a cylindrical portion 53 formed around a throughhole 52 through which the supporting rod 30 passes are formed on thesupporting plate 50. Thus, as it can be prevented that the supportingplate 50 is deflected by the load of the upper polishing plate 2, thedeflection of the upper polishing plate 2 can be further prevented andthe load applied to the works of the carriers can be applied uniformly.

The gyro-mechanism 40 is constituted of first axial rods 41 secured onthe cylindrical holding portion 31, first rings 42 rotatable around thefirst axial rods 41, second axial rods not shown in figures which aresecured on the first rings 42, second rings 43 rotatable around thesecond axial rods not shown in figures, third axial rods 44 secured onthe second rings 43 and third rings 45 rotatable around the third axialrods 44, respectively, and the supporting plate 50 is secured at upperends of the third rings 45. Furthermore, a cover plate 46 is provided atlower ends of the third rings 45. In this embodiment, the first rods 41,the second rods and the third rods 44 are arranged at an angle of 60°one another. Thus, as the supporting plate 50 and the upper polishingplate 2 can be moved in three dimensional direction to the supportingrod 30, a fine gap of the supporting rod 30 and the like can beabsorbed, so that balancing of the upper polishing plate 2 to the lowerpolishing plate 3 can be maintained. Furthermore, each center axis ofthe first rod 41, the second rod and the third rod 44 is positioned atapproximately same height to a polishing surface of the upper polishingplate 2. Namely, the oscillation fulcrum is positioned on a standardplane expanding from the polishing surface of the upper polishing plate2.

Due to the abovementioned constitution, the carriers installing worksare arranged so as to be engaged with the sun gear 4 and the internalgear 5, the upper polishing plate 2 is gone down to the lower polishingplate 3 so as to put the carriers between the upper and the lowerpolishing plates 2 and 3, and then, the upper polishing plate 2, thelower polishing plate 3, the sun gear 4 and the internal gear 5 arerotated in specific in a desired directions respectively, so that bothsides of the works can be polished well. Besides, in this operation,because deflection of the upper polishing plate 2 is restrainedremarkably, balancing of the upper polishing plate 2 can be held andload of the upper polishing plate can be applied to the works in thecarriers uniformly, so that polishing accuracy of the works can beincreased remarkably.

1. A double side polishing machine comprising a rotatable lowerpolishing plate, a rotatable upper polishing plate which goes up anddown to said lower polishing plate by means of an elevation mechanism,carriers putting between said lower and said upper polishing plates andinstalling a plurality of works respectively and a rotation andrevolution mechanism for rotating and revolving said carriers betweensaid lower and said upper polishing plates, wherein a supporting platefor upper polishing plate which suspends said upper polishing plate isconnected to an upper portion of a coupling mechanism is providedoscillatably on vertically movable supporting rod of said elevationmechanism, and wherein an oscillation fulcrum of said coupling mechanismis positioned at approximately same height to a polishing surface ofsaid upper polishing plate.
 2. A double side polishing machine accordingto claim 1, wherein said upper polishing plate is suspended on saidsupporting plate outward in a radial direction from a center of gravityin one side of said polishing surface of said upper polishing plate. 3.A double side polishing machine according to claim 1, wherein thesupporting plate has a plurality of reinforcement ribs extending alongthe radiation direction.
 4. A double side polishing machine according toclaim 2, wherein the supporting plate has a plurality of reinforcementribs extending along the radiation direction.
 5. A double side polishingmachine according to claim 1, wherein said coupling mechanism is agyro-mechanism and a center position of said gyro-mechanism ispositioned at approximately same height to said polishing surface ofsaid upper lapping plate.
 6. A double side polishing machine accordingto claim 2, wherein said coupling mechanism is a gyro-mechanism and acenter position of said gyro-mechanism is positioned at approximatelysame height to said polishing surface of said upper lapping plate.
 7. Adouble side polishing machine according to claim 3, wherein saidcoupling mechanism is a gyro-mechanism and a center position of saidgyro-mechanism is positioned at approximately same height to saidpolishing surface of said upper lapping plate.
 8. A double sidepolishing machine according to claim 4, wherein said coupling mechanismis a gyro-mechanism and a center position of said gyro-mechanism ispositioned at approximately same height to said polishing surface ofsaid upper lapping plate.
 9. A double side polishing machine accordingto claim 1, wherein said upper lapping plate can be rotatable by anupper lapping plate rotation mechanism for rotating said supporting rodand said upper lapping plate rotation mechanism is provided on saidelevation mechanism.
 10. A double side polishing machine according toclaim 2, wherein said upper lapping plate can be rotatable by an upperlapping plate rotation mechanism for rotating said supporting rod andsaid upper lapping plate rotation mechanism is provided on saidelevation mechanism.
 11. A double side polishing machine according toclaim 3, wherein said upper lapping plate can be rotatable by an upperlapping plate rotation mechanism for rotating said supporting rod andsaid upper lapping plate rotation mechanism is provided on saidelevation mechanism.
 12. A double side polishing machine according toclaim 4, wherein said upper lapping plate can be rotatable by an upperlapping plate rotation mechanism for rotating said supporting rod andsaid upper lapping plate rotation mechanism is provided on saidelevation mechanism.
 13. A double side polishing machine according toclaim 5, wherein said upper lapping plate can be rotatable by an upperlapping plate rotation mechanism for rotating said supporting rod andsaid upper lapping plate rotation mechanism is provided on saidelevation mechanism.
 14. A double side polishing machine according toclaim 6, wherein said upper lapping plate can be rotatable by an upperlapping plate rotation mechanism for rotating said supporting rod andsaid upper lapping plate rotation mechanism is provided on saidelevation mechanism.
 15. A double side polishing machine according toclaim 7, wherein said upper lapping plate can be rotatable by an upperlapping plate rotation mechanism for rotating said supporting rod andsaid upper lapping plate rotation mechanism is provided on saidelevation mechanism.
 16. A double side polishing machine according toclaim 8, wherein said upper lapping plate can be rotatable by an upperlapping plate rotation mechanism for rotating said supporting rod andsaid upper lapping plate rotation mechanism is provided on saidelevation mechanism.